This invention relates to an air blowing machine, and more particularly to a portable blower/vacuum unit primarily for yard and garden use.
Portable blower/vacuum units are in common use in many residential areas. In one mode of use, the unit serves as a blower and delivers a high velocity stream of air for gathering leaves, twigs, etc. In another mode of use, the unit serves as a vacuum and is used to collect yard debris such as leaves, twigs, etc. For example, U.S. Pat. Nos. 4,644,606, No. 4,325,163 and No. 5,245,726 show units of this general nature.
Such units include a centrifugal impeller driven by a motor (gasoline or electric), the impeller being mounted in a scroll-shaped housing. The housing has a central air intake opening and a tangential air outlet opening, and the impeller propels the air stream through the housing and out the air outlet opening.
A problem encountered with such a unit when used in the vacuum mode is that debris tends to collect and jam in the air intake opening. The impeller extends close to the housing and the debris may become caught between them.
U.S. Pat. No. 4,325,163 discloses "a chopping or mulching blade 86" which is mounted on the impeller shaft upstream of the impeller, and U.S. Pat. No. 5,245,726 discloses a "cutting structure/cutting attachment 12" which, like the blade 86, is separate from the impeller and is mounted on the impeller shaft. In both of these patents, the blade or attachment is designed to mulch the incoming leaves, and the small particles of the mulch have less tendency to clog or jam the unit. However, a mulching blade in addition to an impeller increases the cost of the assembly.
In another centrifugal fan construction, the Minnard U.S. Pat. No. 1,843,088 shows fan vanes or blades having scoops formed on their radially inner sides, for increasing the capacity of the fan.
It is a general object of the present invention to provide a fan including an improved impeller, which avoids the foregoing problems.